The present invention relates to monitoring equipment comprising a part which defines a cavity, input means to input fluid under pressure into the cavity, mounting means on the said part to enable an engine fuel injector valve or other fluid release device to be connected to the said part and to release fluid from the cavity intermittently when the system is in use, control means connected to issue a triggering signal to the fluid release device to cause the latter to release fluid from the cavity, and a pressure sensor coupled to the cavity to provide a measure of the pressure within the cavity.
Such monitoring equipment is disclosed in our co-pending United Kingdom Patent Application No. 9930120.2 filed on Dec. 21, 1999.
A disadvantage of such equipment is that the pressure as measured by the sensor is given spurious values by virtue of the shock waves following release of fluid from the cavity by the fluid release device.
The present invention seeks to provide a remedy.
Accordingly, the present invention is directed to monitoring equipment having the construction set out in the opening paragraph of the present specification, in which the equipment further comprises pressure signal modifying means connected to receive signals from the pressure sensor and the control means and constructed to provide an output signal which is a measure of the pressure of fluid within the cavity at the time the control means issues such a triggering signal, whilst the effect of signals from the pressure sensor received by the modifying means on the input signal therefrom at other times is obviated.
Advantageously, the input means of the monitoring equipment may include an adjustable flow regulator which serves to regulate the input of fluid under pressure into the cavity.
A substantially constant pressure of fluid within the cavity can be obtained effectively if the adjustable regulator means comprises fluid flow control means coupled to the pressure sensor so that the flow control means effects an increase or a decrease to the flow of fluid into the cavity, thereby to maintain the pressure of the fluid therein at a desired operating pressure.
Preferably, the flow control means comprises an hydraulic amplifier arranged to operate valve means of the flow control means so as to effect such increase or decrease.
An especially fast response to changes of pressure is obtainable if the flow control means comprises a first movable member, transducer means which serves to provide a force which acts on and moves the first movable member in dependence upon the magnitude of an input signal delivered to the flow control means, two inputs connected to deliver pressurised fluid to opposite sides respectively of the first movable member and to opposite sides respectively of a second movable member, and output means from which fluid flows after it has reached the first movable member, in such a manner that movement of the first movable member in a first direction increases the resistance to flow of fluid from one of the two inputs to the said output means, so that pressure of fluid from that input urges the said second movable member in a given direction, whilst movement of the first movable member in a second direction, opposite to the first, increases the resistance to flow of fluid from the other of the said two inputs to the said output means, so that pressure of fluid from that other input urges the said second movable member in another direction opposite to the said given direction, the flow control means further comprising balancing means to balance the movement of the second movable member against the said force, and valve means which are opened to an extent which is dependent upon the position of the second movable member, whereby the extent to which the valve means is opened is dependent upon the magnitude of the input signal, so that the latter effects such increase or decrease.
Advantageously, the pressurised fluid delivered by the said two inputs is the pressurised fluid from the said source.
Preferably, the balancing means comprise a spring.
The valve means of the flow control means is preferably a slide valve, for example a spool valve.
Advantageously, the pressure signal modifying means provides a continuous output signal to the adjustable flow regulator by holding the value it has at the time the control means issues such a triggering signal until the time the control means issues the next such signal.